Add a table of version bumping to the release docs.

RELEASE.md

@@ -2,8 +2,6 @@
 
 This document guides a contributor through creating a release of JupyterLab.
 
-## Check installed tools
-
 Review `CONTRIBUTING.md`. Make sure all the tools needed to generate the
 built JavaScript files are properly installed.
 
@@ -39,6 +37,30 @@ cd jupyterlab
 pip install -ve .
 ```
 
+## How Python and NPM versions increment
+
+Here is an example of how version numbers progress through a release process.
+
+| Command                              |  Python Version Change  | NPM Version change   |
+|---                                   |---                      |---      |
+| `jlpm bumpversion minor`             | x.y.z-> x.(y+1).0.a0    | All a.b.c -> a.(b+1).0-alpha.0 |
+| `jlpm bumpversion build`             | x.y.z.a0-> x.y.z.a1     | All a.b.c-alpha.0 -> a.b.c-alpha.1 |
+| `jlpm bumpversion release`           | x.y.z.a1-> x.y.z.rc0    | All a.b.c-alpha.1 -> a.b.c-rc.0 |
+| `jlpm bumpversion release`           | x.y.z.rc0-> x.y.z       | All a.b.c-rc0 -> a.b.c
+| `jlpm patch:release [...packages]`   | x.y.z -> x.y.(z+1)      | Selected a.b.c -> a.b.(c+1) |
+
+### JS major release(s)
+
+Command:
+`jlpm bump:js:major [...packages]`
+
+Results:
+
+* Python package is not affected.
+* JS dependencies are also bumped a major version.
+* Packages that have already had a major bump in this prerelease cycle are not affected.
+* All affected packages changed to match the current release type of the Python package (`alpha` or `rc`).  
+
 ### Publishing Packages
 
 We use [bump2version](https://github.com/c4urself/bump2version) to manage the Python